Intermittent and Elliptical Inertial Oscillations in the Atmospheric Boundary Layer

Abstract

Abstract As a convective boundary layer over land decays in the late afternoon, the atmosphere responds to the release of turbulent stresses. For many years, this response has been presumed to take the form of an inertial oscillation, a horizontal circulation with a frequency equal to the local Coriolis frequency, though published documentation of inertial oscillations in the atmosphere has been rare. In fact, documentation of inertial oscillations has been more associated with frontal passages than with the evening transition of the atmospheric boundary layer. A month of boundary layer wind profiler data from the Cooperative Atmosphere–Surface Exchange Study-1999 field program is analyzed here with the Hilbert–Huang transform (HHT), which allows analysis of intermittent, nonstationary, and amplitude-varying wave events. Inertial motions are found in this dataset, but neither the onset times of these inertial motions nor the preferred levels of occurrence are consistent with the evening-transition hypothe...